This Application is a U.S. National Phase Application of PCT International Application PCT/JP99/00990.
1. Field of the Invention
The present invention relates to a high-frequency module for use in a mobile telephone and the like and a method of manufacturing the same.
2. Background Art
A conventional high-frequency module will be described below. A typical conventional high-frequency module, as shown in FIG. 10, has substrate 1 made of an insulator of ceramic material or the like with electronic components mounted thereon and metallic shield case 2 is placed over them. On substrate 1, as shown in FIG. 11, there is a temperature-compensated oscillator, having a stable characteristic regardless of ambient temperature changes (used here as an example of the high-frequency module), constructed of integrated circuit 4 bonded by wires 3 and chip capacitor 5 and crystal oscillator (used here as an example of the filter) 6 connected by reflow soldering.
To miniaturize the temperature-compensated oscillator, recess 10 is formed in substrate 7, as shown in FIG. 12, and while integrated circuit 4 is wirebonded to the bottom surface of recess 10 , crystal oscillator 6 placed on the recess 10 so as to cover recess 10. And chip capacitor 5, of a size of 1.0 mm long and 0.5 mm wide, is placed on top surface 12 on the same side and they are reflow-soldered with solder cream 11. By placing crystal oscillator 6 over integrated circuit 4 in the described manner, miniaturization of the high-frequency module has been attained.
The method of fabrication of the prior art high-frequency module, as shown in FIG. 13, comprises:
first step 13 of wire-bonding integrated circuit 4 to the bottom surface of recess 10 of a substrate with a recess therein;
second step 14, following first step 13, of sealing integrated circuit 4 with an bonding material;
third step 15, following second step 14, of curing the bonding material;
fourth step 16, following third step 15, of applying solder cream to the top surface 12 near the recess 10 by printing;
fifth step 17, following fourth step 16, of mounting chip capacitor 5 and crystal oscillator 6 on solder cream 11 applied as above; and
sixth step 18, following fifth step 17, of bonding chip capacitor 5 and crystal oscillator 6 to the side of top surface 12 of substrate 7 by the application of heat.
By mounting crystal oscillator 6 over the integrated circuit 4, more and more miniaturization of high-frequency modules has been attained.
However, while there are demands for still more miniaturized high-frequency modules, the conventional arrangement is unable to meet such demands because of the limit in obtaining a smaller size than sum of the sizes of crystal oscillator 6 and chip capacitor 5.
On the other hand, by virtue of recent progress in semiconductor technology, integrated circuits have become increasingly smaller in size and, at the same time, the flip-chip-mounting technology making use of bump contacts has been developed. Accordingly, mounting of an integrated circuit in a very small space has become possible. Also, such a chip capacitor as small as 0.6 mm long and 0.3 mm wide has become available. Consequently, the area of an integrated circuit or that of a chip capacitor has become smaller than that of a crystal oscillator. Thus, a proposal for a structure meeting above described demand has come to be earnestly desired.
The present invention was made to address the above-mentioned problem, and it is an object of the invention to provide a miniaturized high-frequency module.
An exemplary embodiment of the present invention relates to an integrated circuit and chip capacitors, electrically connected with the integrated circuit, within a recess of a substrate, and, also, to make a filter and the substrate approximately equal in size. Thereby, a miniaturized high-frequency module can be obtained.
In a further exemplary embodiment of the present invention a high-frequency module is characterized in that the chip capacitors are bonded to the filter with solder cream. Since the chip capacitors can be bonded to the filter by printed solder cream thereto, the need for applying solder cream within the recess can be eliminated and, hence, productivity is improved.
In a further exemplary embodiment of the present invention a high-frequency module is characterized in that it constitutes a temperature-compensated oscillator by using a crystal oscillator as a filter and an integrated circuit comprising;
an oscillation circuit,
an output terminal connected to the oscillation circuit,
a temperature compensating circuit,
a frequency control circuit, and
a stabilized power supply circuit connected with a chip capacitor disposed outside the integrated circuit.
Accordingly, a miniaturized high-frequency module as a temperature-compensated oscillator can be obtained.
In a further exemplary embodiment of the present invention a high-frequency module is, characterized in that it constitutes a receiver comprising;
a first input terminal to which a high-frequency signal is input;
an amplifier receiving the signal input to the first input terminal through a first chip capacitor;
a SAW filter receiving an output of the amplifier;
a mixer receiving an output of the SAW filter at one input thereof;
an output terminal to which an output of the mixer is delivered through a second chip capacitor; and
a second input terminal to which a local oscillation frequency to be input to the other terminal of the mixer through a third chip capacitor is applied.
By inputting a high-frequency signal to the first input terminal and a local oscillation frequency to the second input terminal, a miniaturized receiver can be obtained.
In a further exemplary embodiment of the present invention a high-frequency module is, characterized in that it constitutes a transmitter comprising;
an input terminal to which a high-frequency signal is input;
a SAW filter receiving the input signal input to the input terminal through a first chip capacitor;
an amplifier receiving an output of the SAW filter; and
an output terminal to which an output of the amplifier is delivered through a second chip capacitor.
By inputting a modulated signal to the input terminal and connecting a signal delivered from the output terminal to the antenna, a miniaturized transmitter can be obtained.
In a further exemplary embodiment of the present invention a high-frequency module comprises;
a substrate made of an insulator,
a recess formed in the substrate,
a PLL integrated circuit flip-chip-mounted to the bottom surface of the recess,
a voltage-controlled oscillator electrically connected with the PLL integrated circuit and disposed on the top surface of the substrate so as to cover the recess, and
a low-pass filter made up of chip components electrically connected with the PLL integrated circuit, the low-pass filter contained within the recess,
wherein the voltage-controlled oscillator and the substrate are made virtually equal in size.
By containing the flip-chip-mounted PLL integrated circuit and the low-pass filter made up of chip components within the recess, the substrate and the voltage-controlled oscillator can be made virtually equal in size and, hence, a miniaturized high-frequency module can be embodied
The invention set forth in claim 7 is a method of manufacturing a high-frequency module comprising the steps of;
first step of flip-chip-mounting an integrated circuit on a bottom surface of a recess of a substrate with the recess therein;
second step, following first step, of sealing the integrated circuit with bonding material;
third step, following second step, of curing the bonding material;
fourth step, following third step, of applying solder cream to the bottom surface of the recess;
fifth step, following fourth step, of mounting chip capacitors on the applied solder cream;
sixth step, following fifth step, of bonding the chip capacitors by application of heat;
seventh step, following sixth step, of applying solder cream to a top surface of the substrate by printing;
eighth step, following seventh step, of mounting a filter;
and ninth step, following eighth step, of bonding the filter to the top surface by application of heat.
Since solder cream is applied to the bottom surface of the recess at third step, the chip capacitors are mounted within the recess at fourth step, and the chip capacitors are bonded at fifth step, a miniaturized high-frequency module can be obtained.
In a further exemplary embodiment of the present invention a method of manufacturing a high-frequency module is characterized by including a process for preparing a first component comprising the steps of;
first step, of flip-chip-mounting an integrated circuit on a bottom surface of a recess of a substrate with the recess therein;
second step, following first step, of sealing the integrated circuit with an bonding material;
third step, following second step, of curing the bonding material; and
fourth step, following third step, of applying solder cream to the top surface of the substrate on the side of the recess by printing; and
a process for preparing a second component separate from the process for preparing the first component comprising;
first step of applying solder cream to a filter by printing;
second step, following first step, of mounting chip capacitors on the solder cream applied by printing; and
third step, following second step, of bonding the chip capacitors by the application of heat;
and steps of mounting the second component on the top surface of the substrate of the first component and bonding, thereafter, the components with each other by the application of heat.
Since the chip capacitors are mounted on the filter in the process for preparing the second component, solder cream can be applied by printing and, hence, productivity is improved.
The invention set forth in claim 9 is a method of manufacturing a high-frequency module characterized by including a process for preparing a first component comprising;
first step of flip-chip-mounting an integrated circuit on a bottom surface of a recess of a substrate with the recess therein;
second step, following first step, of sealing the integrated circuit with an bonding material; and
third step, following second step, of curing the bonding material;
and, applying solder cream to a filter by printing which is separate process from the processes for preparing the first component;
fourth step of mounting the first component and chip capacitors on the solder cream applied on the filter by printing; and
fifth step, following fourth step, of simultaneously bonding the chip capacitors and the first component by the application of heat.
Since the chip capacitors and the first component can be simultaneously bonded at fifth step, productivity is improved further.
Exemplary embodiments of the present invention will be described with reference to the drawings.